The present invention relates to a tensioning device for at least one trailing rope of an elevator installation. Within the meaning of the invention, a trailing rope can also be a compensating rope, a compensating chain, or similar flexible connection. The terms xe2x80x9cverticalxe2x80x9d and xe2x80x9chorizontalxe2x80x9d relate to the direction of travel of the elevator. xe2x80x9cVerticalxe2x80x9d means the direction essentially parallel to the direction of travel of the elevator, and xe2x80x9chorizontalxe2x80x9d means the direction essentially perpendicular to it. The term xe2x80x9cfluidxe2x80x9d means some sort of gas or some sort of liquid.
Tensioning devices for trailing ropes have long been known, and are primarily used on traction elevators. The purpose of the tensioning device is, inter alia, to guide the trailing ropes, tension the trailing ropes, limit rope vibrations, increase traction, and prevent the counterweight or elevator car from jumping when the safety gear of the car or counterweight is actuated, or when the car or counterweight strikes the buffer. At speeds of 3.5 m/s and above, the tensioning device must be fitted with an anti-rebound device. Present-day anti-rebound devices consist, for example, of safety gears which trip when the tensioning device moves upward by a specified amount. Just this specified amount has disadvantageous effects. The trailing ropes are tensioned by the jumping counterweight (elastic members) and accelerate the counterweight as it falls back down. The forces that occur when the counterweight falls back onto the suspension rope are also correspondingly large. Moreover, with this known solution, when once the safety gear has tripped, the tensioning device has to be released manually. Only trained personnel are allowed to release it. The need for manual release is due to the system.
Investigations carried out using simulation have shown clearly that almost entirely undamped tensioning devices influence the characteristics of the installation negatively.
Damped tensioning devices are known, and have the advantage that when required they remove energy from the system, as a result of which the energy of the counterweight is reduced as it falls back down.
The U.S. Pat. No. 4,522,285 shows an anti-rebound device in which the vertical motion/damping of the trailing rope tensioning pulley is controlled by a hydraulic system. The system comprises a cylinder and a piston that moves inside the cylinder and divides the cylinder into two chambers. The piston rod is connected at one end to the piston, and at the other end to the tensioning pulley. Due to the one-sided arrangement of the piston rod, the displacement volume on the side of the piston with the piston rod is smaller than on the side where there is no piston rod. To balance the volume/pressure of the two chambers, outside the cylinder there is a container filled with hydraulic fluid, which works actively in conjunction with the two chambers.
A disadvantage of this known construction is the complicated arrangement of the valves, and the inevitable necessity of an externally acting compensating container, which causes the construction of the tensioning device to be costly and complicated.
The present invention concerns a tensioning device for at least one trailing rope that does not possess the aforementioned disadvantages, allows a simple construction, and needs no external compensation container. Damping of the tensioning device is achieved by simple means.
A further advantage is to be seen in that the tensioning device according to the present invention can be manufactured inexpensively.
A further advantage of the present invention is that the cylinder and piston rod form a guide system for the tensioning device.